Tricking LIDARS and robocars
Submitted by brad on Sat, 2015-09-12 12:18Much press has been made over Jonathan Petit's recent disclosure of an attack on some LIDAR systems used in robocars. I saw Petit's presentation on this in July, but he asked me for confidentiality until they released their paper in October. However, since he has decided to disclose it, there's been a lot of press, with truth and misconceptions.
There are many security aspects to robocars. By far the greatest concern would be compromise of the control computers by malicious software, and great efforts will be taken to prevent that. Many of those efforts will involve having the cars not talk to any untrusted sources of code or data which might be malicious. The car's sensors, however, must take in information from outside the vehicle, so they are another source of compromise.

There are ways to compromise many of the sensors on a robocar. GPS can be easily spoofed, and there are tools out there to do that now. (Fortunately real robocars will only use GPS as one clue to their location.) Radar is also very easy to spooof -- far easier than LIDAR, agrees Petit -- but their goal was to see if LIDAR is vulnerable.
The attack is a real one, but at the same time it's not, in spite of the press, a particularly frightening one. It may cause a well designed vehicle to believe there are "ghost" objects that don't actually exist, so that it might brake for something that's not there, or even swerve around it. It might also overwhelm the sensor, so that it feels the sensor has failed, and thus the car would go into a failure mode, stopping or pulling off the road. This is not a good thing, of course, and it has some safety consequences, but it's also a fairly unlikely attack. Essentially, there are far easier ways to do these things that don't involve the LIDAR, so it's not too likely anybody would want to mount such an attack.
Indeed, to do these attacks, you need to be physically present, near the target car, and you need a solid object that's already in front of the car, such as the back of a truck that it's following. (It is possible the road surface might work.) This is a higher bar than attacks which might be done remotely (such as computer intrusions) or via radio signals (such as with hypothetical vehicle-to-vehicle radio, should cars decide to use that tech.)
Here's how it works: LIDAR works by sending out a very short pulse of laser light, and then waiting for the light to reflect back. The pulse is a small dot, and the reflection is seen through a lens aimed tightly at the place the pulse was sent. The time it takes for the light to come back tells you how far away the target is, and the brightness tells you how reflective it is, like a black-and-white photo.
To fool a lidar, you must send another pulse that comes from or appears to come from the target spot, and it has to come in at just the right time, before (or on some, after) the real pulse from what's really in front of the LIDAR comes in.
The attack requires knowing the characteristics of the target LIDAR very well. You must know exactly when it is going to send its pulses before it sends them, and thus precisely (to the nanosecond) when a return reflection ("return") would arrive from a hypothetical object in front of the LIDAR. Many LIDARS are quite predictable. They scan a scene with a rotating drum, and you can see the pulses coming out, and know when they will be sent.





It's important to understand the nominating and voting on the Hugos is done by members of the World SF Society, which is to say people who attend the World SF Convention (Worldcon) or who purchase special "supporting" memberships which don't let you go but give you voting rights. This is a self-selected group, but in spite of that, it has mostly manged to run a reasonably independent vote to select the greatest works of the year. The group is not large, and in many categories, it can take only a score or two of nominations to make the ballot, and victory margins are often small. As such, it's always been possible, and not even particularly hard, to subvert the process with any concerted effort. It's even possible to do it with money, because you can just buy memberships which can nominate or vote, so long as a real unique person is behind each ballot.